It is suggested that the keratinolytic activity of proteases are associated with the degrading activity of the abnormal type prion protein (PrPSc). We tried to analyze the keratinolytic properties of the PrPSc- degrading enzyme E77. E77 showed a much greater keratinolytic activity than proteinase K and subtilisin. The maximum activity of keratin was observed at a pH value of 12.0 at 65°C. E77 also showed a pH-independent adsorbability for keratin. These profiles of E77 were the same as the PrPSc -degrading enzyme NAPase, except for high alkaline conditions. E77 and NAPase showed lower collagenolytic and elastinolytic specificities.